3 week old peep vomiting, weak, still eating and drinking...

I have 17 chicks that were hatched in a 3rd grade classroom. They are 3 weeks old and have been doing well. They are feed the chick starter- recommended by my feed store and I've been including durvet High Performance Poultry Pak (water-soluble vitamin and electrolyte mix for poultry) in their water- diluted as directed or even a bit more so as they are growing fine.

The problem I am having is that this morning when I went to check on my peeps I noticed that 12 of them had their eyes shut and when I closely inspected them I thought it may have been from their water mixture- their beaks were yellowish and clumpy looking. I searched the internet and found that they would be well served to have their faces washed and eye medicine put in them. I did that.

I carefully washed their eyes with a soft cloth and put the eye medication gently into their eyes. They opened and the peeps seemed happy and fine. One little peep had a very dirty face and crust on his little beak that was like the others- but more. I made sure to clean his little face all up- had a heater going in the bathroom so that they would be warm even when the warm water on thier faces turned cooler, and then returned them to their pen. Their pen is large and has 2 corners with heat lamps, a nice little area for practicing perching, and fresh food and water. I clean the pine shaving floor every other day. I put all of the peeps into their house and sat in with them a while to make sure they were ok with the eye medicine in their eyes, and not too upset by the face washing.

The little extra crusty peep went under the light and laid down. I watched him for a bit- he seemed to dry nicely and have a nice rest. He got up and drank some vitamin water and ate a few little bites of food, then opened his mouth really big and threw up. Next, he ran to the warm lighted area and looked like he was in distress- bubbles started popping out of his mouth. I picked him up and he was all shivery. I held him until he calmed down, wiped his beak and hurried down to find out if anyone knows what I should do to help this chick. He seems weak. He is a bit smaller than his coop mates. Any suggestions will be greatly appreciated. I noticed too, when I picked him up to wash him that his little neck was already wet- I don't know how long he has been throwing up- and if that is why his neck is wet. He wasn't throwing up yesterday.
Thank you! Mia

I'd stop the vitamins. They may be overdosing on Vitamins A & D since most commercial chick starter feed also contains those vitamins. The Durvet vitamin/electrolyte supplement is meant to be used for birds during times of reduced feed - like when they're sick and not eating much (or at all).

Thoroughly wash out the water fount and give them tepid water (not cold) with nothing added to it. Then, mix up a "mush" of chick crumbles with a little warm water and add a tsp. or two of plain yogurt. Feed this to all the chicks 3 times a day. At the same time, leave the dry chick crumble feeder available so they can eat in between times. Give no other snacks, treats, or grit for the next couple of days. Keep them in the brooder, too, no outside time until you see some improvement.

If any chicks continue to throw up or stop drinking, you can give them Pedialyte instead of the fresh water, but no vitamins.